The /tmp/tce/optional directory contains all of those tcz packages from the current release. If I configure /opt/bootsync.sh with those extensions using a su tc -c "tce-load -i package.tcz" command they all load; I'd prefer to integrate them more tightly with the OS and put them directly into onboot.

I have remaster unpack / pack scripts and am creating a modified core.gz each time I make changes to the underlying operating system in order to persist.

Your structure is correct, it's the fact that /tmp/tce was not intended for remastered extension loading, but as a runtime RAM location. The path intended for such embedding was /tmp/builtin.

Beautiful! I had to create /tmp/builtin and then I copied my /tmp/tce/optional folder into /tmp/builtin/optional. After that I created /tmp/builtin/onboot.lst and listed all the tcz packages that are in the /tmp/builtin/optional directory. Very nice!